Parallel Loads - More or Less exactly the same as using AC Out2 ?

richardimorserichardimorse Registered Users Posts: 98 ✭✭
As I understand it, the only difference is the meter, Parallel loads provides a mechanism to split power demand off at the utility point of supply where the main utility branching DB board is usually located, as opposed to the inverter location (AC Out 2) which may be somewhere remote from this location, also using parallel loads with a meter provides a benefit over AC OUT2, in that that they show up on the GX console as a separate "Loads" box whereas the AC OUT2 power total is combined on the GX with AC OUT1 as "Critical Loads" (only 1 current sensor).

Inside the Victron this is controlled by relays which make and break the connection to AC IN and OUT2, the make and break connections are outside of the Victron when Parallel loads are used and can achieve equal, if not better results, because with parallel loads on a low battery condition you can switch them back to the utility (before the meter) instead of disconnecting them from power completely as is frequently done with AC OUT2 using VE config.  

The question is does the Victron limit power production (from battery or from an AC coupled Fronius or from a DC coupled MPPT charge controller) to what it sees as the total power demand on its internal current sensor or does it limit power production to what it sees as the total power demand on the external current sensor (in this case an external Carlo Gavazzi 10A meter), I think the answer is the external meter, hence parallel loads function more or less the same as AC OUT2, with a few added benefits.

Lets take an example, a small farm, with a main "branching" distribution board at the point of utility supply (actually used for geographic distribution) which connects to 2 sub-main DB Boards (at separate geographic residential clusters) which in turn connect to Load DB Boards in each building, so the load MCBs are 2 steps removed from the point of utility supply.

The Victron system will power any parallel loads from its battery and other power sources and will stop doing this when Loss of Mains occurs, if you are using MultiPlus II this decision is made inside the inverter, parallel loads (because AC IN is disconnected) and AC Out 2 are load shed

If you are using Quattro / Ziehl this is more complicated for instance, even though the Quattro is not certified for anti islanding, it will attempt to cut off AC IN unless LoM detection is disabled in VE Config - the Ziehl is supposed to be doing this for the Quattro.

If you stop the Quattro from disconnecting the input, then the point of mains disconnection is where the Ziehl disconnect contactor is placed.

SO here is the layout and power cable discussion points

Now my point is - that it may not be exactly true (as stated in the picture) that the entrance property can not be protected, because the Quattro can be prevented from disconnecting the power and hence leaves it up to the ziehl therefore the point of utility disconnect can (in this case) be upstream of the "branch off" for the other geographic locations, then the other locations would continue to receive power as normal from the Quattro after the Ziehl has cut off the utility supply on mains power failure.

In my mind the easy option and the best option is to install a 2nd expensive power cable from the utility supply (80A - 50kVA) to wherever the inverters are located and that may well be the best approach, rather than attempting to compromise and complicate the installation.

Comments

  • Dave AngeliniDave Angelini Solar Expert Posts: 5,910 ✭✭✭✭✭
    I would check Victron as much of their equipment was not UL listed a few years back. If that is important for your county inspections.
    This is really not offgrid is it?
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • richardimorserichardimorse Registered Users Posts: 98 ✭✭
    edited April 22 #3
    I see your point and it is very much about how the system is described on the local authority grid connection application, with the Quattro (1 ENS) not being on "the approved list" it could get rejected, even if its LoM function is disabled and it is used with a Ziehl and parallel loads, effectively as a UPS, even if the grid connected parts are the Fronius PV Inverter and Ziehl which are on the approved list (2 ENS).  

    Perhaps to be on the safe side 6 * MultiPlus II 5 kVA would certainly pass local authority inspection as opposed to 3 * 10kVA Quattro, the savings on using MultiPlus II would offset additional utility power cable costs making the installation a low risk option for everyone.

    We would like to take the system "Off-Grid" to avoid the cost penalty of a rural electricity connection of approx US $ 600 per month before you use anything, but on the other hand is US $ 600 per month too much to pay for peace of mind, even if you don't use any utility power, it is good to know that it is there, I guess this is a gradual confidence building process and would involve investing in generator technology.  

    By the time you pay generator maintenance costs, keeping the utility power line may be a better option at US $ 600 per month, even if it is not used at all and the system operated in "Off Grid" mode without actually "pulling the plug"
  • richardimorserichardimorse Registered Users Posts: 98 ✭✭

    This is really not offgrid is it?
    I should have posted this under the "Grid Integrated" topic
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,910 ✭✭✭✭✭
    No big deal to me, I just was busy with other things and did not have time to really read and understand your situation.

    No matter what you do, the math for not just the cost either way, but also adding in the loss in value of dropping the utility.
    It could make the property less valuable and also harder to sell someday.

    So this really is about Offgrid and the utility value which can be a hard to put a number on.

    I like to ask my clients what is important to you? If you really love the place and can afford to keep it up then dive in. Living Offgrid is kind of like long term heath insurance, if you have enough funds, you do not need insurance. If you are poor, the government will/might take care of you. 
    If you are in the "middle class"  You might not want to go thru losing your lifestyle and becoming poor. The insurance might be worth it.

    Speaking of government, where are you? Africa? Jolly old England?  Also what kind of KWH (your usage) are we talking about here? Those pumps might use more than you think. Anything can be done offgrid these days! There is a price though! Good Luck on your journey through this. You can get some good ideas from the other members here :)
    .


    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • richardimorserichardimorse Registered Users Posts: 98 ✭✭
    I am in Africa, Cutting the Utility cord can be done at any time, so I will leave that as a later decision to be made by the owners of the Farm, I am probably going to take the following approach, Install 1*45 meters of 4-Core 16mm (4-AWG) SWA from the new inverter location to DB Board C at the main buildings and 155m of 4-Core 16mm (4-AWG) back to the main DB board which is oversized for supplemental Utility power only really needs 6mm 10-AWG cable, but allows for future EV charging (owner has plans for EV) on the basis of "do it once"
  • richardimorserichardimorse Registered Users Posts: 98 ✭✭

    what kind of KWH (your usage) are we talking about here? Those pumps might use more than you think. Anything can be done offgrid these days! There is a price though! 
    I tried to install a Cerbo GX, 12V DC power supplies, zigbee extenders at the main buildings and and some 100/5A CTs with a 10A Carlo Gavazzi meter at the main DB last week, but ran out of time the farm is in a really rural area so 5 hours round trip by car, I will go back next week and finish off, the kWH is 3000 per month but no idea how that is used until the meters finish installation
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